Digital image sensors, such as CMOS or CCD sensors, include a plurality of photosensors each configured to convert photons incident upon the photosensors (“captured light”) into electric charge. The electric charge can then be converted into image data representing the light captured by each photosensor. The image data includes a digital representation of the captured light, and may be manipulated or processed to produce a digital image capable of display on a viewing device. Image sensors are implemented in integrated circuits (“ICs”) with a physical surface that may be divided into a plurality of pixel regions (for instance, one or more photosensors and attendant control circuitry) configured to convert light into an electrical signal (charge, voltage, current, etc.). For convenience, pixel regions within an image sensor may also be referred to as image pixels (“IPs”) and the aggregate of the pixel regions or image pixels will be referred to as the image sensor region. An image sensor IC typically will also include areas outside of the image sensor region, for example certain types of control or interface circuitry.
Most CMOS image sensors contain A/D (analog-to-digital) circuitry to convert pixel electrical signals into image data. The A/D circuitry can be one or more ADCs (analog-to-digital converters) located at the periphery of the image sensor region. Particularly for one-bit (binary) quantization, it is also possible to distribute one-bit ADCs within the image sensor region, one per IP or group of IPs.